ChiNext, China's Nasdaq-style stock market, opened with a roar as its initial batch of companies logged gains of as much as 210%, underscoring China's investors' appetite for new listings. At the end of the day, the market capitalization of ChiNext as a whole stood at 140 billion yuan ($20.5 billion), more than double the 68.6 billion yuan total based on the firms' IPO prices.

The explosive debut, which left the exchange's stocks trading at around 100 times earnings, comes as broader concerns that lower interest rates, huge fiscal stimulus and a growing appetite for risk amid improvements in the global economy are causing potentially dangerous asset bubbles across Asia. Property and stock markets in China and other countries have been rising quickly, and China has seen an increase in inflows of speculative hot money.

Within hours of the trading start, all 28 ChiNext stocks had risen to the point where one after the other they were forced into temporary trading halts by the Shenzhen Stock Exchange, which hosts the upstart venue.

All the ChiNext stocks finished the day with robust gains, led by Chengdu Geeya Technology Co., a cable- and digital-TV equipment maker, which rose 210% to 35 yuan from its initial public offering price of 11.30 yuan. The other 27 stocks logged gains ranging from 76% to 195%.

The share gains fueled concerns that the exchange would mirror the performance that tends to define new listings in China: large initial gains followed by a brutal pullback.

A Shanghai-based individual investor said he sold all his ChiNext-listed shares on Friday, on concerns the stocks' high valuations wouldn't be sustainable. I had expected the stocks to rise, he said, but I hadn't realized that they could rise that much.

ChiNext was set up as a fund-raising venue for small, innovation-driven firms, which were largely closed out of China's recent lending boom.